15,411 people have died of covid in NYC, though excess death numbers suggest that this is an undercount and it's more like 19,200. [1] The population of NYC is 8.4M. If everyone in NYC had been exposed this would give a death rate of ~0.18%, or ~0.23% after adjusting for excess deaths. Antibody tests say ~21% [2] of the population has had it, so multiply by 5 and it looks like if everyone got it about 1% of people would die. That's about 10x more deadly than the flu.
[1] https://www.nytimes.com/interactive/2020/04/21/world/coronav...
[2] https://www.nytimes.com/2020/04/23/nyregion/coronavirus-anti...